Instead of preventing on which domain a website may be iframed, is it possible to restrict the domains that are allowed to be iframed on the current website?

The reasoning behind this would be security (preventing impersonation of a legitimate iframe to trick the user into entering details and stealing these), although I'm not quite sure yet if it would actually improve security or only creates an easily avoidable complexity layer for an attacker, since apparently something else is compromised already.

Also there's probably a challenge when first loading an allowed iframe url which then navigates to a disallowed url.